2,3-carboxy alkoxy succinic acid and salts thereof

ABSTRACT

α,α&#39;-carboxyalkoxy succinic acids and salts thereof are described in which the carboxyalkoxy radicals contain from 2 to about 7 carbon atoms and which are useful as sequestrants and in which the carboxyalkoxy radicals contain from about 8 to about 30 carbon atoms and which are useful as lubricant additives, sizing agents for paper and textiles, and the like. A method is disclosed for sequestering polyvalent metal ions using α,α&#39;-carboxyalkoxy succinic acid or salts thereof. A method for sequestering polyvalent metal ions is disclosed using α,α&#39;-carboxyalkoxy succinic acid or salts thereof in combination with a surfactant.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 385,545, filed Aug. 3, 1973,now U.S. Pat. No. 3,980,578 which in turn is a continuation-in-part ofapplication Ser. No. 153,816, filed June 16, 1971, now U.S. Pat. No.3,784,486.

BACKGRUND OF THE INVENTION

In the manufacture of detergent formulations for laundering and generalpurpose washing operations, it is common practice to employ detergentbuilders-substances used in combination with surface-active compounds toaid in cleansing the articles being washed. The polyphosphates, notablysodium tripolyphosphate and tetrasodium pyrophosphate, are the commonlyused detergent builders. However, these materials possess a seriousshortcoming. For example, the phosphorus residues resulting from thewidespread use of synthetic detergent formulations containing thesephosphorus-containing builders have been said to contribute toeutrophication of rivers, lakes, underground streams, and other bodiesof water. ["Detergent Phosphorus Effect on Algae" by Thomas E. Maloney,Journal of the Water Pollution Control Federation, Vol. 38, No. 1, pp.38-45 (January 1966)]. To appreciate the magnitude of the problem, ithas been estimated that over two billion pounds of salts of condensedphosphates are used in detergents each year in the United States. Thephosphorus-containing builders can therefore by properly termedubiquitous.

Further there is also at present a growing need for low costsequestering agents efficiently operable over wide pH ranges (7-10). Theuse of sequestering agents to remove metal ions or to reduce metal ionconcentrations is well known to the scientific community. For example,sequestering agents are used in metal cleaning processes, leathertanning, textile processes, the stabilization of dyes and vegetablesoils, laundering and other washing operatons, and the processing ofbeer. Most of the sequestering agents used today are efficient only at ahigh pH (9-10). In addition some of the best known sequestering agentssuch as sodium tri-polyphosphate suffer from the eutrophication problemsdiscussed above.

Thus, there is a need for a compound which is an effectivenon-phosphorus detergent builder and is also an effective sequestrantover a wide pH range. Accordingly, it is an object of this invention toprovide a detergent builder system which is devoid of the eutrophiccharacteristics exhibited by the polyphosphates and other phosphorusbuilders. Further, it is an object of this invention to provide washingcompositions which are devoid of phosphorus-containing builders butwhich possess the advantageous characteristics of washing compositionswhich presently contain the polyphosphate builders. Another object ofthis invention is to provide a sequestering agent which is effectiveover a wide pH range.

Other important objects of this invention will become apparent from theensuing description and appended claims.

THE INVENTION

One embodiment of this invention involves the provision ofα,α'-carboxyalkoxy succinic acid and the water-soluble salts thereof. Aswill be apparent from the ensuing description, these new compounds areof considerable utility in the chemical and allied arts. By way ofexample, the compounds of this invention in which the carboxyalkoxyradicals contain from 2 to about 7 carbon atoms are especially useful assequestrants and as detergent builders. The compounds of this inventionin which the carboxyalkoxy radicals contain from about 8 to about 30carbon atoms are of utility as lubricant additives, sizing agents forpaper and textiles, and the like. The preferred compounds for treatingcellulose, such as sizing paper and fabrics or fibers and for use asdispersants and detergents in lubricating oil for gasoline and dieselengines generally contain from about 10 to about 20 carbon atoms in eachcarboxyalkoxy radical.

Thus another embodiment of this invention provides an aqueous solutionwhich contains a sequestrant selected from the group consisting of: (a)α,α'-carboxyalkoxy succinic acid, wherein the carboxyalkoxy radicalscontain from 2 to about 7 carbon atoms, (b) water soluble salts of saidacids; and (c) mxitures of (a) and (b).

A further embodiment involves the method of sequestering sequesterablemetal ions in an aqueous solution which comprises introducing into saidsolution a sequestrant composition selected from the group consistingof: (a) α,α'-carboxyalkoxy succinic acid, wherein the carboxyalkoxyradicals contain from 2 to about 7 carbon atoms, (b) water soluble saltsof said acids; and (c) mixtures of (a) and (b). In this method it isdesirable to also introduce into the solution a surfactant selected fromthe group consisting of anionic detergents, cationic detergents,nonionic detergents, ampholytic detergents, zwitterionic detergents andmixtures thereof, the ratio by weight of the surfactant to thesequestrant being from about 10:1 to about 1:10.

In accordance with another facet of this invention, it has been foundpossible to reduce-indeed, eliminate-the phosphorus-containing buildersin detergent formulations without sacrifice of cleaning power andbrightness by employing a detergent builder selected from the groupconsisting of:

(a) α,α'-carboxyalkoxy succinic acids wherein the carboxyalkoxy radicalscontain from 2 to about 7 carbon atoms;

b. water soluble salts of said acids; and mixtures of (a) and (b).

Generaly, the acids of this invention which may be used as sequestrantsor builders have the formula: ##STR1## wherein R is a carboxyalkoxyradical having from 2 to about 7 carbon atoms and wherein R' is acarboxyalkoxy radical having from 2 to about 7 carbon atoms. Examples ofvarious α,α'-carboxyalkoxy succinic acids which are effective asbuilders are: α,α'-(1-carboxyethoxy) succinic acid,α,α'-carboxyisobutoxy succinic acid, α,α'-(1-carboxypentoxy) succinicacid, α-(2-methyl-3-carboxybutoxy)-α'-carboxymethoxy succinic acid,α,α'-(1-carboxyhexoxy succinic acid,α-carboxyisobutoxy-α'-(1-carboxyethoxy) succinic acid and the like. Themost preferred acid has been found to be α,α'-carboxymethoxy succinicacid.

As before mentioned water soluble salts of the α,α'-carboxyalkoxysuccinic acids of this invention are also useful sequestrants anddetergent builders. The preferred salts are the mono, di, tri, and tetraalkali metal salts of such acids due to their relative inexpensivenessand stability. Examples of such useful salts are α,α'-carboxymethoxysuccinic acid, monosodium salt; α,α'-carboxymethoxy succinic acid,tetrasodium salt; α,α'-(1-carboxyethoxy) succinic acid, monosodium salt;α,α'-carboxymethoxy succinic acid, tetrapotassium salt;α,α'-(1-carboxyethoxy) succinic acid, dipotassium salt;α-(1-carboxymethoxy)-α'-(1-carboxyethoxy) succinic acid, trirubidiumsalt; α,α'-carboxyisobutoxy succinic acid, dilithium salt;α,α'-(1-carboxyhexoxy) succinic acid, monocesium salt, and the like.Normally the sodium or potassium salts will be found most useful.However, other salts may be found suitable such as the ammonium salts,alkylammonium salts, or the like. The alkaline earth metal salts,particularly the calcium salts, are useful intermediates in certainprocesses for producing the alkali metal salts or the acids.

The builders of this invention can be advantageously used with a widevariety of detergent actives or surfactants, including those known inthe art as anionic, cationic, nonionic, ampholytic, and zwitterionicdetergents as well as any suitable mixture of such detergents. When theresultant washing compositions are used in aqueous washing systems, thecleaning power of the formulation is enhanced in much the same way aswhen the commonly used polyphosphate builders are employed. Yet thepresent builder systems do not contribute to the eutrophication problemscharacteristic of phosphorus-containing builders.

Accordingly, this invention provides a washing composition composed ofan organic detergent surfactant suitable for use in water and, as abuilder, either α,α'-carboxyalkoxy succinic acids wherein thecarboxyalkoxy radicals contain from 2 to about 7 carbon atoms,water-soluble salt of such acids, or mixtures of the before mentionedacids and salts. Although the proportions may be varied to suit theneeds of the occasion, the weight ratio of the detergent surfactant tothe builder of this invention will normally fall within the range ofabout 10:1 to about 1:10. A preferred range is from about 1:1 to about1:6. The weight ratio of detergent surfactant to builder will of coursebe on the low side of the before mentioned range whenever utilizing abuilder of high molecular weight and vice versa.

The builder of this invention may be added to the system as a salt or anacid or a mixture thereof. When it is desired to operate a system havinga high pH (about 9-10) the salts may be added as they render thesolution basic. On the other hand, when operating under acidicconditions the acidic form of the builder is added to the washingcomposition. Of course when it is desired to operate within anintermediate range (pH of about 7) the acid and the salt may be bothutilized. Another mode of addition involves merely adding the acid orthe salt and subsequently adjusting the pH of the system by adding baseor acid respectively. For example, a system having a high pH can beobtained by adding the acid form of the builder and then neutralizingthe system with a base.

It has been found that the best building action takes place at high pH,i.e. of about 10. However, it has been found that the particularbuilders of this invention are still very effective in essentiallyneutral systems.

As noted above, the builders of this invention can be used with a widevariety of detergents including those classed in the art as anionicdetergents, cationic detergents, nonionic detergents, ampholytic (i.e.amphoteric) detergents, and zwitterionic detergents, and any suitablemixture of two or more of these (whether from the same class or fromdifferent classes). The anionic surface-active compounds are generallydescribed as compounds which contain hydrophilic and lyophilic groups intheir molecular structure and which ionize in an aqueous medium to giveanions containing the lyophilic group. Typical of these compounds arethe alkali metal salts of organic sulfonates or sulfates, such as thealkali metal aryl sulfonates and the alkali metal salts of sulfates ofstraight chain primary alcohols. Sodium dodecylbenzene sulfonate andsodium lauryl sulfate are typical examples of these anionicsurface-active compounds (anionic synthetic detergents). For a furtheramplification of anionic organic detergents which can be successfullybuilt in accordance with this invention, reference should be had to U.S.Pat. No. 3,422,021, particularly the passage extending from Column 11,line 47 through Column 12, line 15, including the references thereincited, which passage is incorporated herein as if fully set out in thisspecification.

The cationic detergents are those which ionize in an aqueous medium togive cations containing the lyophilic group. Typical of these compoundsare the quaternary ammonium salts which contain an alkyl group of about12 to about 18 carbon atoms, such as lauryl benzyl dimethyl ammoniumchloride. Compounds of this nature are used in detergent formulationsfor special purposes; e.g., sanitizing and fabric softening.

Nonionic surface-active compounds are generally described as compoundswhich do not ionize in water solution. Often times these possesshydrophilic characteristics by virtue of the presence therein of anoxygenated chain (e.g., a polyoxyethylene chain), the lyophilic portionof the molecule being derived from fatty acids, phenols, alcohols,amides or amines. Exemplary materials are the poly-(ethylene oxide)condensates of alkyl phenols (e.g., the condensation product formed fromone mole of nonyl phenol and ten moles of ethylene oxide), and thecondensation products of aliphatic alcohols and ethylene oxide (e.g.,the condensation product formed from 1 mole of tridecanol and 12 molesof ethylene oxide). Reference should be had to U.S. Pat. No. 3,422,021,especially the passage extending from Column 12, line 16 through Column13, line 26 where a fairly extensive discussion and exemplification ofnonionic synthetic detergents is set forth. Inasmuch as the nonionicsynthetic detergents set forth in that passage can be successfully builtin accordance with this invention, the foregoing passage is incorporatedherein as if fully set out in this specification.

The ampholytic surfactants are compounds having both anionic andcationic groups in the same molecule. Exemplary of such materials arederivatives of aliphatic amines which contain a long chain of about 8 toabout 18 carbon atoms and an anionic water solubilizing group, e.g.,carboxysulfo, sulfo or sulfato. Examples of ampholytic detergents aresodium-3-dodecylaminopropionate, sodium-3-dodecylaminopropane sulfonate,sodium N-methyl taurate, and related substances such as higher alkyldisubstituted amino acids, betaines, thetines, sulfated long chainolefinic amines, and sulfated imidazoline derivatives.

Zwitterionic synthetic detergents are generally regarded as derivativesof aliphatic quaternary ammonium compounds, in which the aliphaticradical may be straight chain or branched and wherein one of thealiphatic substituents contains from about 8 to 18 carbon atoms and onecontains an anionic water solubilizing group, e.g., carboxy, sulfo, orsulfato. Examples of compounds falling within this definition are3-(N,N-dimethyl-N-hexadecyl ammonio)-propane-1-sulfonate and3-(N,N-dimethyl-N-hexadecyl ammonio)-2-hydroxypropane-1-sulfonate. For astill further appreciation of surface-active compounds (syntheticdetergents) which can be employed in the practice of this inventionreference may be had, for example, to the disclosures of U.S. Pat. No.2,961,409 and French Pat. No. 1,398,753.

For a very extensive disclosure of surfactants in general see U.S. Pat.No. 3,526,592 and the various U.S. Patents referred to therein. Inasmuchas the surfactants set forth in these above patents are compatible withthe builders of this disclosure, the foregoing patents are incorporatedherein as if fully set out in the specification.

Finished detergent formulations of this invention may contain minoramounts of other commonly used materials in order to enhance theeffectiveness or attractiveness of the product. Exemplary of suchmaterials are soluble sodium carboxymethyl cellulose or other soilredeposition inhibitors; perfume; fluorescers; dyes or pigments;brightening agents; enzymes; water; alcohols; other builder additives,such as the water-soluble salts of ethylenediaminetetraacetic acid,N-(2-hydroxyethyl)-ethylenediaminetriacetic acid, nitrilotriacetic acidand N-(2-hydroxyethyl)-nitrilodiacetic acid; and pH adjusters, such assodium hydroxide and potassium hydroxide. In the built liquid detergentformulations of this invention, the use of hydrotropic agents may befound efficacious. Suitable hydrotropes include the water-soluble alkalimetal salts of toluene sulfonic acid, benzene sulfonic acid, and xylenesulfonic acid. Potassium toluene sulfonate and sodium toluene sulfonateare preferred for this use and will normally be employed inconcentrations ranging from about 2 to 10 percent by weight based on thetotal composition.

It will be apparent from the foregoing that the compositions of thisinvention may be formulated according to any of the various commerciallydesirable forms. For example, the formulations of this invention may beprovided in granular form, in liquid form, in tablet form or in the formof flakes or powders.

The relative proportions and absolute quantities of the severalingredients of the finished compositions of this invention aresusceptible to variation and in most cases will vary depending upon suchfactors as the nature of the particular ingredients being utilized, theend use for which the composition is intended to be put, the relativecosts of the ingredients, and the like. For example, the totalconcentration of the detergent formulations of this invention in waterwill normally range below about 0.15 percent by weight although it isentirely feasible to utilize higher concentrations where thecircumstances warrant or justify the use of higher concentrations. Inmost cases the aqueous washing solutions of this invention will containfrom about 0.1 to about 0.2 weight percent combined detergent active(s)and builder. The preferred compositions of this invention arephosphorus-free although it may be desired to include therein reducedquantities of conventional phosphorus-containing materials such assodium tripolyphosphate, tetrasodium pyrophosphate, salts of substitutedmethylene diphosphonic containing materials such as sodiumtripolyphosphate, tetrasodium pyrophosphate, salts of substitutedmethylene diphosphonic acids, long chain tertiary phosphine oxides, orthe like.

The invention is not to be limited to any particular method of mixingthe builder and the detergent. The builder may be mechanically mixed in,crutched in the detergent in the form of a slurry, or dissolved in asolution of the detergent. In addition, the builder system may beadmixed with the detergent in any of the forms in which the detergent ismanufactured, as well as being added simultaneously or separately to anaqueous solution. In any event, the present builder system is intendedto be used with the detergent at the time of application as a cleansingagent.

A further embodiment of this invention encompasses the use of eitherα,α'-carboxyalkoxy succinic acids wherein the carboxyalkoxy radicalscontain from 2 to about 7 carbon atoms, the water soluble salts thereofor mixture of the salt and acid as sequestering agents. The preferredsalts are the alkali metal salts. Of these salts sodium and potassiumare most preferred. Other useful salts are the ammonium salts, thealkylammonium salts, the alkanol ammonium salts, and the like.

The concentration of the above mentioned acids and salts in any givensolution will of course be dependent to some extent upon theconcentration of the substance to be sequestered. Thus amounts rangingfrom trace quantities up to about 500 ppm or more are permissible.

In general, the amount of sequestrant used is an amount sufficient tochelate to a desired extent with whatever is in the water to bechelated. Thus the amount of sequestrant in aqueous solution generallyranges from a trace up to a saturation amount. Preferably, the amount ofsequestrant ranges from about 10 parts per billion up to about 50,000parts per million. The higher amounts are generally used in treatment ofindustrial waste streams and the like. For water treatment where theamount of material to be chelated is generally smaller than withindustrial wastes the amount of sequestrant ranges from about 10 partsper million to about 500 parts per million. An even more preferrednarrower range is from about 50 to about 200 parts per million, with thenation-wide average of 120 parts per million being typical andfrequently preferred.

A unique feature exhibited by the above described sequestrants of thisinvention is that they are effective sequestrants in systems having a pHrange of from about 3 to about 10.

A typical example of a system in which such sequestrants are veryvaluable is an aqueous detergent solution. In such solutions, a widevariety of detergents or surfactants, including anionic, cationic,nonionic, ampholytic, and zwitterionic detergents, as well as manysuitable mixtures of such detergents may be used in conjunction with thesequestrants of this invention. The prior description of thesedetergents and surfactants found in this specification in conjunctionwith the builder action of the compounds of this invention is likewiseapplicable to the sequestering function of these compounds.

In washing systems the weight ratio of surfactant to sequestrant rangesfrom about 10:1 to about 1:10. Preferred ratios are within the range offrom about 1:1 to about 1:6.

A preferred embodiment in this invention is the sequestration of calciumand magnesium ions in an aqueous medium. However, various other metalions may also be sequestered. Sequesterable metal ions in generalinclude the polyvalent metals of Groups I-B, II-A, II-B, III-A, III-B,IV-A, IV-B, V-A, V-B, VI-A, VI-B, VII-B and VIII of the Periodic Chart(Fisher Scientific Co., 1955). For example, iron, copper, aluminum,chromium, nickel, manganese, cobalt, tin, and vanadium may also besequestered pursuant to this invention. Preferably the sequesteredsubstance is calcium or magnesium. Solvents may be present in theaqueous solution of sequestrant, preferred solvents being polar solventssuch as lower alcohols, ketones and carboxylic acids. Thus, typicalco-solvents are ethyl alcohol, acetone and acetic acid.

In some applications and uses of the compositions of the presentinvention, it is desirable to have α,α'-carboxyalkoxy succinic acidcompounds in which each of the carboxyalkoxy groups has more than 7carbon atoms, such as from about 8 to about 30 carbon atoms. In general,these compounds can be prepared by processes similar to those used forproducing the compounds whose carboxyalkoxy groups each contain from 2to about 7 carbon atoms, attention being given to the use of anappropriate starting material to contribute the desired carboxyalkoxygroup.

Typical compounds of this group include the following acids:α,α'-(carboxyoctoxy) succinic acid, α,α'-(carboxydecoxy) succinic acid,α,α'-(carboxydodecoxy) succinic acid, α,α'-(carboxytetradecoxy) succinicacid, α,α'-(carboxyhexadecoxy) succinic acid, α,α'-(carboxyoctadecoxy)succinic acid, α,α'-(carboxyeicosoxy) succinic acid,α,α'-(carboxypentacosoxy) succinic acid, and α,α'-(carboxytriacontoxy)succinic acid. Useful salts of these acids include those having cationsset forth hereinbefore for the acids and salts having from 2 to about 7carbon atoms per carboxyalkoxy group.

In order to still further illustrate the practice of this invention, thefollowing examples are presented.

EXAMPLE I

A preferred built formulation of this invention had the followingcomposition:

    ______________________________________                                                           Weight Percent                                             ______________________________________                                        Dodecylbenzene sulfonate                                                                           20.0                                                     (a typical linear alkyl                                                       benzene sulfonate)                                                            Sodium silicate (ratio                                                                              6.0                                                     SiO.sub.2 :Na.sub.2 O of 2.4:1)                                               Sodium carboxymethyl  0.6                                                     cellulose                                                                     Sodium sulfate       33.4                                                     α,α'-carboxymethoxy succinic                                                           40.0                                                     acid                                                                                               100.0                                                    ______________________________________                                    

The performance of this detergent composition was evaluated by use ofthe standard Launder-Ometer test. In particular, the formulation wasdissolved in water to a concentration of 0.15 weight percent and the pHof the solution adjusted to 9.5 with small amounts of sodium hydroxidesolution. The water had a hardness of 150 ppm (Ca/Mg 3/2). Swatches ofstandard artificially soiled cloth were subjected to the washingprocedure. The Launder-Ometer bath temperature was fixed at 120° F. andthe washing span was 10 minutes. After washing, the samples were removedfrom the washing solution and thoroughly rinsed with pure water. Afterdrying, the whiteness of the cloths was ascertained by use of a standardcommercially available reflectance photometer. The identical procedurealso was employed with a formulation identical to that described abovewith the exception that sodium tripolyphosphate was used in lieu of theα,α'-carboxymethoxy succinic acid.

In these tests it was established that the formulation of this inventionwas essentially as effective as the corresponding sodiumtripolyphosphate formulation. In particular, the cloths washed with theformulation of this invention had a whiteness of 95 ± 6 compared to thewhiteness of the same kind of soiled cloths washed in the sodiumtripolyphosphate formulation (assigned the value of 100 percent).

EXAMPLE II

The same procedure was followed as in Example I except that water havinga hardness of 300 ppm (Ca/Mg 3/2) was used. It was found thatα,α'-carboxymethoxy succinic acid gave a whiteness of 94 percent ± 6 ascompared to the assigned value of a 100 percent for sodiumtripolyphosphate.

EXAMPLE III

Seven grains of calcium (calculated as calcium carbonate) were added toa gallon of water. To this solution α,α'-carboxymethoxy succinic acidwas added so as to prepare a percent solution of the acid. The pH wasadjusted to 10 by the addition of sodium hydroxide. The residual calciumwas then measured using a standardized calcium electrode. A reduction to0.7 grains per gallon of calcium was noted indicating that 6.3 grainsper gallon had been sequestered.

EXAMPLE IV

The same procedure was followed as in Example III except that the pH wasadjusted to 7. Upon measurement of the remaining calcium it was foundthat 1.6 grains of calcium per gallon remained thus indicating that 5.4grains of calcium per gallon were sequestered.

Generally speaking, the builders and sequestrants of this invention canbe made by the reaction of an α-diazo ester containing up to 7 carbonatoms in the carboxyl structure and a tartrate ester followed by thesaponification of the resultant product. Similarly, theα,α'-carboxyalkoxy succinic acid structure useful as lubricantadditives, sizing agents, etc. containing from 8 to 30 carbon atoms percarboxyalkoxy group are prepared using the appropriate α-diazo ester,such as ethyl diazooctylate plus a tartrate ester. More particularly, toa 25 percent solution tartrate ester (1 mole) and diethyl ether, 5weight percent (based on the weight of the ester) of freshly distilledBF₃ -etherate is added. The solution is cooled from room temperature toabout 5° C. After cooling about 1 mole of the α-diazo ester is added tothe solution. The solution is stirred until N₂ evolution hassubstantially ceased and then is allowed to come to room temperature.The unreacted reactants are separated from the product by washing thesolution with a 5 percent NaHCO₃ solution followed by drying anddistillation. Saponification of the recovered α,α'-carboxyalkoxysuccinic acid tetraalkyl ester with a calculated amount of caustic,i.e., aqueous NaOH, yields a salt of α,α'-carboxyalkoxy succinic acid.The exact composition of the carboxyalkoxy radical found in the saltwill of course depend upon the particular reactants used. For example,if a carboxymethoxy radical is desired then the tartrate ester should bediethyl tartrate and the α-diazo ester should be ethyl diazoacetate. Toobtain the acid forms of the builder and sequestrants of this inventionthe above salts are merely neutralized with a mineral acid such as HCl,H₂ SO₄ etc.

As noted above, the builders and sequestrants of this invention may beused in combination with other builders or sequestrants. Suchcombinations offer the opportunity for enhanced cost effectiveness orsuperior results, or both. Among the builders or sequestrants which maybe combined with those of this invention are the water soluble salts ofsuch acids as citric acid (e.g., trisodium citrate, tripotassiumcitrate, etc.), diglycolic acid (e.g., disodium diglycolate, dipotassiumdiglycolate, etc.), nitrilotriacetic acid (e.g., trisodiumnitrilotriacetate, tripotassium nitrilotriacetate, etc.), oxydisuccinicacid (e.g., tetrasodium oxydisuccinate, tetrapotassium oxydisuccinate,etc.), and the like, as well as mixtures of two or more of such salts.If desired, the free acids (e.g., citric acid, diglycolic acid,nitrilotriacetic acid, oxydisuccinic acid, or mixtures of two or more ofthese acids) may be used in combination with the builders orsequestrants of this invention. Combinations in which there is nonitrogen or phosphorous containing ingredient are particularly preferredfrom the ecological standpoint. When using such combinations the ratiosof the builders or sequestrants may be varied within relatively widelimits although generally speaking the weight ratio between the builderof this invention and the builder used therewith will fall within therange of from about 0.1:1 about 10:1, and most preferably from about0.25:1 to about 4:1.

We claim:
 1. α,α'-carboxyalkoxy succinic acid and the water solublesalts thereof.
 2. The composition of claim 1 wherein the carboxyalkoxyradicals contain from 2 to about 7 carbon atoms.
 3. The composition ofclaim 1 wherein the carboxyalkoxy radicals contain 2 carbon atoms. 4.Salt compositions in accordance with claim 1 wherein the salts arealkali metal salts, alkaline earth metal salts, ammonium, alkyl ammoniumsalts.
 5. Salt compositions in accordance with claim 1 wherein the saltsare alkali metal salts.
 6. Salt compositions in accordance with claim 1wherein the salts are sodium or potassium salts.
 7. A salt compositionin accordance with claim 1 wherein the salt is a sodium salt ofα,α'-carboxymethoxy succinic acid.
 8. A salt composition in accordancewith claim 1 wherein the salt is a potassium salt of α,α'-carboxymethoxysuccinic acid.
 9. A salt composition in accordance with claim 1 whereinthe salt is α,α'-carboxymethoxy succinic acid, tetra sodium salt orα,α'-carboxymethoxy succinic acid, tetra potassium salt. 10.α,α'-carboxymethoxy succinic acid.